Precision pyrotechnic display system and method having increased safety and timing accuracy

ABSTRACT

A system and method are disclosed for controlling the launch and burst of pyrotechnic projectiles in a pyrotechnic, or “fireworks”, display.

REFERENCE TO PENDING PRIOR PATENT APPLICATIONS

This patent application:

(1) is a continuation-in-part of pending prior U.S. patent applicationSer. No. 10/958,721, filed Oct. 5, 2004 by George Bossarte et al. forPRECISION PYROTECHNIC DISPLAY SYSTEM AND METHOD HAVING INCREASED SAFETYAND TIMING ACCURACY (Attorney's Docket No. MAG-4 DIV CON), which is inturn a continuation of prior U.S. patent application Ser. No.10/313,879, filed Dec. 6, 2002 by George Bossarte et al. for PRECISIONPYROTECHNIC DISPLAY SYSTEM AND METHOD HAVING INCREASED SAFETY AND TIMINGACCURACY (Attorney's Docket No. MAG-4 DIV), which is in turn adivisional of prior U.S. patent application Ser. No. 09/281,203, filedMar. 30, 1999 by George Bossarte et al. for PRECISION PYROTECHNICDISPLAY SYSTEM AND METHOD HAVING INCREASED SAFETY AND TIMING ACCURACY(Attorney's Docket No. MAG-4), which in turn claims the benefit of (i)U.S. Provisional Patent Application Ser. No. 60/079,853, filed Mar. 30,1998 by Paul McKinley for ELECTRONIC PYROTECHNIC IGNITER OFFERINGPRECISE TIMING AND INCREASED SAFETY (Attorney's Docket No. MAG-1 PROV),and (ii) U.S. Provisional Patent Application Ser. No. 60/095,805, filedAug. 7, 1998 by Paul R. McKinley et al. for PRECISION PYROTECHNICDISPLAY SYSTEM HAVING INCREASED SAFETY AND TIMING ACCURACY (Attorney'sDocket No. MAG-2 PROV); and

(2) claims the benefit of pending prior U.S. Provisional PatentApplication Ser. No. 60/616,159, filed on Oct. 5, 2004 by Craig Boucheret al. for ELECTRONIC PYROTECHNIC IGNITERS (Attorney's Docket No. MAG-5APROV).

The six (6) above-identified patent applications are hereby incorporatedherein by reference.

FIELD OF THE INVENTION

This invention relates to the control of the launch and burst ofpyrotechnic projectiles in a pyrotechnic display. More particularly, theinvention relates to the use of electronic components for the purpose ofimproving the accuracy of the timing of both the launch and the burst ofthe pyrotechnic projectiles. The invention further relates to the use ofelectronic components for the purpose of increasing the safety of boththe pyrotechnic operator and the viewing audience.

BACKGROUND OF THE INVENTION

The professional fireworks industry has employed black powder-basedpyrotechnic ignition systems for many years. These systems typically usea black powder fuse—cotton string or cord impregnated with blackpowder—to ignite a “lift” charge, which propels the projectile high intothe air. The ignition of the lift charge also ignites a second blackpowder fuse, which provides a time delay to allow the projectile toreach a desired height above the ground. After the time delay of thefuse, the “break” charge is ignited, causing the particular visual orauditory effect of the pyrotechnic projectile.

Although black powder-based ignition systems are relatively easy to use,the fundamental limitations of the black powder fuse prevent theindustry from achieving the timing accuracy and repeatability necessaryfor precisely choreographed pyrotechnic displays. This is because theburn rate—and hence the delay time—for a black powder fuse can varyconsiderably depending on the fabrication of the fuse, the particularmaterials used in the construction of the fuse, and on other parameterssuch as the temperature of the fuse at the time of ignition. U.S. Pat.No. 5,627,338 by Poor et al. teaches that the typical accuracy of thetime delay of a black powder fuse is on the order of +/−16%. Controllingthe delay time for a black powder fuse to better than +/−1% is extremelydifficult; and even if this accuracy could be reliably achieved, itwould still contribute to a total variability of 100 milliseconds for a5-second fuse. That is, a +/−1% variation would cause a 5-second fuse tovary by +/−0.05 seconds, or a total variability of 100 milliseconds.Tests with pyrotechnic audiences have shown that most people can detecttiming differences as small as 20 milliseconds, and half the people candetect timing differences as small as 10 milliseconds. Thus, in order toachieve precisely choreographed displays for certain types ofpyrotechnic shells, particularly shells with a short burst time, thevariability of the fuse's time delay must be held to better than 10milliseconds, and preferably to about 1 millisecond. A variability of 1millisecond represents an additional factor of 100, or +/−0.01% accuracyfor a 5-second fuse. Achieving such accuracy is impossible with blackpowder fuses.

In addition, the inherent limitations of the black powder fuse alsoprovide a source of potential failures that present real risk to boththe display operators and the proximate audience. Pyrotechnic shells canbe manufactured with the lift and break charges protected relativelywell from external sources of accidental ignition by the use ofprotective layers around the charges. However, the use of a black powderfuse for the lift charge necessitates the exposure of the black powderto the external environment of the shell. Consequently the shell becomesmuch more sensitive to false ignition by burning materials from nearbypyrotechnic shells, resulting in unintentional “crossfire”. If the liftcharge of a shell is ignited but the time delay fuse to the break chargeburns too slowly, a “hangfire” occurs, in which the shell explodes as itreturns to the ground, often near the display operator or in theaudience. Even more dangerous, if a hangfire explodes after the shellhits the ground, both the explosion and the falling shell itself presentsignificant risks to the operator and audience. If a fuse fails toignite the lift charge, but the fuse continues to burn and ignites thebreak charge while the shell is still on the ground, a “mortar burst”can occur, and the ignition products of the break can potentially ignitethe break charges of all the adjacent shells of the display. A breakcharge being ignited on the ground can result in serious injury to theoperating personnel as well as the destruction of the entire display.

A number of alternatives have been proposed to eliminate black powderfuses or to improve their reliability. The most notable of theseinvolves the use of electrically operated ignition devices, commonlycalled “electric matches” or “e-matches”. The construction and ignitionof various forms of e-matches are described in U.S. Pat. Nos. 5,544,585by Duguet, 5,123,355 by Hans et al., 4,409,898 by Blix et al., 4,354,432by Cannavo' et al., 4,335,653 by Bratt et al., 4,267,567 by Nygaard etal., and 4,144,814 by Haas et al.

The use of an e-match to replace the black powder fuse for igniting alift charge has the advantage that the exposed electrical wires are notsusceptible to false ignition by sparks or other ignition by-products.Such use of the e-match reduces the likelihood of crossfires, but doesnothing to improve the timing of the break since a black powder delayfuse would still be required to ignite the break charge. On the otherhand, U.S. Pat. Nos. 5,627,338 by Poor et al., 5,623,117 by Lewis,5,499,579 by Lewis, 5,335,598 by Lewis et al., 4,363,272 by Simmons,4,239,005 by Simmons, and 4,068,592 by Beuchat describe methods to delaythe firing action of an e-match based on electrical or pyrotechnicdelays, but none of these methods are suitable to achieving the highaccuracy required for choreographed displays. A method of using ane-match is described by Poor et al. in U.S. Pat. No. 5,627,338, but eventhis technique is limited to about 25 milliseconds variability, which isstill a factor of 25 worse than the desired 1 millisecond variabilitypreviously discussed.

A number of problems or faults can occur during the setup of achoreographed pyrotechnic display. The pyrotechnic operator cannoteasily detect many of these problems. If e-matches are used to replacethe black powder fuses, new problems unique to e-matches are possible.For example, if e-matches are used to ignite the black powder liftcharges, the electrical connections to the e-matches may be faulty. Acommon practice by the industry is to connect multiple e-matches to thesame ignition source to allow multiple shells to be fired at the sametime. Such multiple connections are done either in parallel or inseries.

If multiple e-matches are wired in parallel to a single electricalignition source, the possibility exists that some e-matches will not beconnected properly. On the other hand, if multiple e-matches are wiredin series, the possibility exists that the electrical ignition sourcewill be insufficient to ignite all of the e-matches.

If e-matches are used to ignite both the lift and break charges,additional problems may develop. For example, either or both of thee-matches may have broken wires. Furthermore, since an energy source isrequired to fire both e-matches (and the source for the break match musttravel with the projectile), the possibility exists that either energysource may be insufficient to ignite its corresponding e-match. If, forexample, the lift energy source is sufficient to ignite the lift charge,but the break energy source is not sufficient to ignite the breakcharge, a dangerous hangfire can result, with significant risk to thepyrotechnic operator and the audience.

Accordingly, a definite need exists for a method and system forlaunching and detonating pyrotechnic displays, which is capable ofaccuracy on the order of 1 millisecond, particularly for conventionalshells that use black powder for the lift charge. A need also exists forincreasing the safety for both the pyrotechnic operator and the viewingaudience for conventional black powder shells. A need also exists forincreasing the safety for pyrotechnic shells that use e-matches toignite the charges. The present invention satisfies these requirementsand additionally provides further related advantages.

OBJECTS AND SUMMARY OF THE INVENTION

In a broad sense, the present invention describes a method and systemfor controlling the launch and burst of pyrotechnic projectiles in apyrotechnic display. More particularly, the present invention describesa method and system for increasing the safety and improving the accuracyof ignition timing for pyrotechnic displays.

An object of the present invention is to provide a system capable ofachieving ignition timing accuracy to better than 1 millisecond forpyrotechnic displays. A further object of the present invention is toachieve such accuracy in ignition timing for pyrotechnic displays thatuse conventional black powder for the lift charge. An additional objectof the present invention is to achieve such accuracy in ignition timingfor pyrotechnic displays that use means other than black powder, such aspneumatic power, for launching the pyrotechnic projectile.

A further object of the present invention is to provide the capabilityto use standard pyrotechnic projectiles with black powder fuses forsome, but not all, of the pyrotechnic display. Thus pyrotechnicoperators can mix pyrotechnic shells utilizing the present inventionwith more conventional pyrotechnic shells in order to achieve the mostcost-effective pyrotechnic display possible.

A further object of the present invention is to increase the safety ofthe pyrotechnic display for both the pyrotechnic operator and theviewing audience. A further object of the present invention is to reducethe potential of misfires and crossfires (i.e., the ignition of aprojectile by the ignition products of nearby shells) by eliminating thetraditional black powder fuse. A further object of the present inventionis to reduce the potential of hangfires (i.e., shells that explode afterreturning to the ground).

A further object of the present invention is to provide the capabilityof reporting to the pyrotechnic operator the existence of faults withinthe system and to indicate which shells will not have their lift chargeignited because of the presence of these faults.

A further object of the present invention is to provide the capabilityto use multiple shells on the same ignition output and to provide thecapability of reporting to the pyrotechnic operator the existence offaults in any of the individual shells.

While the present invention is presently intended primarily for use inimproved pyrotechnic displays, the invention's advantages of increasedsafety and timing accuracy may be applied to other fields as well, suchas construction and explosive demolition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a mortar with a pyrotechnic shell that contains an ignitermodule of the present invention.

FIG. 2 shows a block diagram of a complete pyrotechnic display systemillustrating one embodiment of the present invention.

FIG. 3 shows the block diagram of an igniter module of a preferredembodiment of the present invention.

FIG. 4 shows the block diagram of one embodiment of the interface moduleof the present invention.

FIG. 5 shows a flow chart for the system logic including thecommunications between the interface module and the igniter module inone embodiment of the present invention.

FIG. 6 shows the detailed schematic of the igniter module for oneembodiment of the present invention.

FIG. 7 shows details of bi-directional communications, over a singlepair of wires, between the igniter and the interface module.

FIG. 8 shows the detailed schematic of the igniter module for a secondembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention involves a system and method for controlling thelaunch and burst of pyrotechnic projectiles in a pyrotechnic, or“fireworks,” display.

Pyrotechnic Projectile

FIG. 1 shows a typical pyrotechnic projectile 1 placed in mortar 2.Projectile 1 utilizes load cord 3 to allow the pyrotechnic operator toeasily place the projectile into mortar 2. Embedded inside projectile 1is igniter 4 which is connected to the lift electric match (e-match) 5and to the break e-match 6. Wires 7 connect igniter 4 to the pyrotechniccontrol system. Lift e-match 5 is embedded in lift charge 8, which istypically made of black powder. Lift charge 8, when ignited, providesthe force to propel projectile 1 high into the air. Break e-match 6 isembedded in break charge 9, which is also typically made of blackpowder. Break charge 9, when ignited by break e-match 6, causesprojectile 1 to burst and provide the visual or auditory effect desired.Projectile 1 may contain additional pyrotechnic materials, such as stars10, which enhance the visual or auditory effect of the projectile.

Control System

FIG. 2 shows a block diagram of the control system. Control panel 11 isa manual control board which would be used by the pyrotechnic operator.Control panel 11 includes a key switch 12 for enabling the firing of thepyrotechnic shells. Use of key 13 allows the operator to remove the keyto prevent accidental firing of the shells. The front panel of controlpanel 11 includes indicators 14, typically incandescent lamps or lightemitting diodes (“LED's”), which provide information on the status ofthe individual channels, or “cues.” The term “cue” has come into popularusage because of the interest in synchronizing the burst of thepyrotechnic projectiles with music. Although FIG. 2 shows five cues onthe front panel, in practice the control panel 11 will typically havemany more cues, possibly as many as 20 to 40. Control panel 11 alsoincludes switches 15 that allow individual cues to be enabled forignition at a particular time. The pyrotechnic operator will select oneor more cues for ignition, observe the status of the cues, and thenpress firing button 16, which initiates the ignition of the launch ofthe pyrotechnic shells for the enabled cue(s). After the firing of thepreviously-selected cue(s), the operator will select the next cue andagain press the Firing Button 16 in order to initiate the launch of theshell or shells for that cue. By sequencing through the cues, theoperator is able to use control panel 11 and firing button 16 to controlthe entire pyrotechnic display.

In FIG. 2, cable 17 connects control panel 11 to interface module 20.Interface module 20 contains electronics that receive firing signalsfrom control panel 11 and generates the necessary control voltages tofire the igniters 4 in the pyrotechnic shells (FIG. 1). These controlvoltages are passed through cable 21 to a distribution panel 22.Interface module 20 includes additional display indicators 23 and 24which provide information to the pyrotechnic operator of the status ofeach of the cues. Since interface module 20 is located closer to thepyrotechnic shells than control panel 11, the display indicators 23 and24 are used primarily during set up of the pyrotechnic display in orderto verify that the system is wired properly. Interface module 20 alsoincludes key switch 25 and key 26 to ensure that no power is applied toany igniter 4 while people are loading the shells into the mortars.Interface module 20 is powered by battery 27 through cable 28.

Distribution panel 22 includes connectors 29, which allow the operatorto hook up wires 7 (FIGS. 1 and 2) to connect the igniters 4 to thecontrol system.

Control panel 11 is assumed to be built in accordance with pyrotechnicindustry standards for manual control boards. Specifically, any currentapplied to cable 17 for the purpose of measuring electrical continuityin a lift e-match 5 would be less than 50 milliamperes. Any currentapplied to cable 17 for the purpose of igniting lift e-match 5 would begreater than 250 milliamperes.

FIG. 2 also shows an optional computer system 31 that would be used in asecond preferred embodiment. Computer system 31 includes keyboard 32 andmonitor 33, which is connected to interface module 20 by cable 34.Computer system 31 would be used for automatically sequencing the firingof the projectiles in response to a computer program in coordinationwith other effects such as music. Manual control panel 11 would not beused if computer system 31 were controlling the pyrotechnic display.

In a third preferred embodiment (not shown), interface module 20 anddistribution panel 22 are combined into a single package. Thisembodiment eliminates the need for cable 21 and provides a more compactassembly.

Igniter

FIG. 3 shows a block diagram of igniter 4, which would be used for allthree embodiments discussed above (i.e., a system utilizing manualcontrol panel 11; a system utilizing computer system 31 in place ofmanual control panel 11; and a system combining interface module 20 anddistribution panel 22 into a single package). FIG. 3 also shows lifte-match 5 and break e-match 6. Wires 7 connect igniter 4 to theremainder of the pyrotechnic control system. Igniter 4 contains fourfunctional blocks, i.e., transient protector 40, polarity detector 41,energy storage element 42, and control and timing circuitry 43.

The purpose of transient protector 40 is to prevent electrostaticdischarges or other transient high-voltage events from passing on to theremainder of igniter 4 and possibly damaging igniter 4 or accidentallyfiring either lift e-match 5 or break e-match 6.

Polarity detector 41 ensures that voltages are of the proper polarityand currents flow to the igniter circuitry regardless of the polarity ofwires 7. Referring back to FIG. 2, polarity detector 41 allows theoperator to connect a pair of wires 7 to the corresponding pair ofconnectors 29 without regard to polarity. The use of polarity detector41 thus simplifies the wiring task for the pyrotechnic operator and,more importantly, reduces the possibility of wiring errors.

The third functional block for igniter 4 is energy storage element 42,which preferably comprises a capacitor. Recalling that igniter 4 isembedded in pyrotechnic projectile 1, when the projectile is launched bythe ignition of lift charge 8, wires 7 will be broken. Thus, igniter 4will be electrically separated from the distribution panel 22 and anysource of energy, such as battery 27. Therefore, in order to ignite thebreak e-match 6, a source of energy must travel with projectile 1.Although energy storage element 42 could be a battery, the use of acapacitor is preferred for several reasons. First, a capacitor can weighless than a battery. Second, a battery tends to be more expensive than acapacitor. Third, the capacitor is preferred for environmental reasons.Fourth, and most important, the use of a capacitor ensures that there isno source of ignition energy for either of the e-matches 5, 6 unless thepyrotechnic operator has intentionally provided the energy from battery27 by use of key switch 25. The use of a capacitor for energy storageelement 42 thus reduces the possibility of accidental ignition of theprojectile 1 and increases the safety of the total system.

The fourth and final functional block for igniter 4 is the control andtiming circuitry 43, which is a microprocessor-based electronic circuitthat is responsible for the ignition of the lift e-match 5 and breake-match 6. The control and timing circuitry 43 includes embeddedsoftware, or “firmware”, which receives information from interfacemodule 20 concerning the desired time for ignition and returnsinformation back to interface module 20 regarding the status of igniter4. As is discussed in greater detail below, the firmware includes bothsafety and timing features. These features preferably includeverification of the following: (1) both lift e-match 5 and break e-match6 are connected properly; (2) no ignition takes place unless both lifte-match 5 and break e-match 6 are verified electrically; (3) no ignitiontakes place unless sufficient energy is stored in energy storage element42 to ensure proper ignition; (4) after the lift e-match 5 is ignited,launch is verified by loss of input power from wires 7; (5) breake-match 6 is not ignited unless launch has been verified; (6) noignition of break e-match 6 will occur after a maximum time delay (toprevent hangfires); and (7) the timing of ignition of break e-match 6occurs within 1 millisecond after the programmed delay followingignition of lift e-match 5 (i.e., the shell bursts within 1 millisecondof its intended time).

It should be appreciated that, with respect to the timing delay betweenactivation of lift e-match 5 and break e-match 6, this timing delay caneither be (1) pre-programmed into the embedded software, or “firmware”,of the igniter's control and timing circuitry 43, or (2) programmed intoigniter 4 at the time of use by the control system, e.g., by computersystem 31.

Interface Module

As shown in FIG. 4, the block diagram of interface module 20 includessix functional blocks.

Front panel 50 of interface module 20 includes fault indicators 23 andready indicators 24 that show the status of each of the system cues.Fault indicators 23 and ready indicators 24 can be made fromincandescent lamps, light emitting diodes (LED's), or other suitablevisible devices. Front panel 50 also includes key switch 25 and key 26which can be used by the pyrotechnic operator to enable or disableignition of the pyrotechnic shells. By putting key switch 25 into the“Safe” position and removing key 26, the pyrotechnic operator can ensurethat no ignition is possible while pyrotechnic projectiles 1 are beinginstalled in mortars 2.

The second functional block of interface module 20 is input currentdetector 51, whose purpose is to detect if any electrical current isbeing drawn from cable 17 (FIG. 2) for any cue. Furthermore, inputcurrent detector 51 determines if the current is less than 50 milliamps(corresponding to a continuity test) or is greater than 250 milliamps(corresponding to a Fire command).

The third functional block for interface module 20 is output controlswitch 52, whose purpose is to communicate if any igniters 4 areconnected to the particular cue. Such communication is bi-directional innature. Output control switch 52 is further responsible for providingcontinuity current (less than 50 milliamps) and firing current (greaterthan 250 milliamps) if standard lift e-matches 5 are directly connectedto the cue.

The fourth functional block for interface module 20 is controller 53, amicroprocessor-based circuit that supervises the entire operation ofinterface module 20. Controller 53 receives input information from inputcurrent detector 51 and generates output signals for output controlswitch 52. Controller 53 also receives status information from igniters4 and communicates that status information back to the control panel 11through input current detector 51. Controller 53 further reads the stateof key switch 25 and displays status information on front panel display50. Additional details of the communication between interface module 20and other parts of the pyrotechnic control system are discussed below.

If the pyrotechnic display is being controlled by computer system 31,rather than control panel 11, communications between controller 53 andcomputer system 31 are handled by I/O module 54.

The final functional block of interface module 20 is power converter 55,which draws power from battery 27 and provides regulated voltages forthe remaining functional blocks of interface module 20.

System Logic Flow

FIG. 5 shows the system logic flow diagram, including interactionbetween interface module 20 and igniters 4. The use of microprocessorsin both interface module 20 and in each igniter 4 allows diagnostics tobe performed in multiple locations and further provides for a high levelof communication between different microprocessors. Furthermore, eachmicroprocessor is capable of performing tests to verify that commandsare consistent with operating conditions. For example, themicroprocessor in each igniter 4 is able to determine if all conditionsnecessary for a successful launch and burst of the pyrotechnicprojectile are being satisfied and is further able to communicate thatinformation back to interface module 20.

Upon power-up, interface module 20 executes a series of self-tests toconfirm that all operating parameters, including input and output ports,are functioning properly. If so, interface module then examines itsindividual output ports to determine if any igniters 4 are connected. Ifan igniter(s) 4 is found, interface module 20 applies a current-limitedvoltage to igniter(s) 4 and requests status information. Shouldinterface module 20 not receive a “valid igniter” response on any portfor which it previously detected the presence of an igniter 4, it willdisable, and signal a “fault” condition for, that particular port.Should interface module 20 detect multiple igniters 4 on a given port,it will instruct all igniters 4 on that port to generate a random numberwithin a certain range as an identification (ID) number. It will thenpoll the port, sequentially stepping through subsets of the designatedrange, to ascertain the individual ID of each igniter 4. Should morethan one igniter 4 return an ID within any one range subset, interfacemodule 20 will instruct all igniters 4 within that subset to re-generatea new random number ID within the range of that subset. Interface module20 will then re-evaluate the igniters 4 utilizing a higher resolution.This process will repeat until each igniter 4 is assigned a unique IDnumber. All further communications between interface module 20 and eachigniter 4 utilize this ID to ensure unique igniter communications.

In one embodiment of the present invention, the operating frequency ofigniter 4 is controlled by a resistor and capacitor combination. Sinceresistors and capacitors are generally not of high accuracy, theresulting frequency will vary from one igniter 4 to another. Since thetime delay of igniter 4 is generated by counting cycles of its operatingfrequency, the time delay will depend directly on the value of theresistor and capacitor. In order to improve the accuracy of the timedelay, interface module 20 next sends a timing calibration sequence toeach igniter 4. This sequence includes an accurately controlled pulse,400 milliseconds in the preferred embodiment, which is measured by eachigniter 4. The igniter 4 counts cycles of its operating frequency duringthe controlled pulse and reports the number of counts back to interfacemodule 20. This process allows interface module 20 to indirectly measurethe operating frequency of each igniter 4 and to verify that thefrequency is within acceptable limits. If the operating frequency of anyigniter 4 is outside the acceptable limits, interface module 20 willdisable the respective output port and signal a “fault” condition.Assuming that the calibration sequence produces measurements within theacceptable limits, igniter 4 will then use the results of themeasurement of the controlled pulse to compensate for the inaccuracy ofthe operating frequency and to modify the pre-programmed time delay toimprove the overall accuracy of the system. Then, as long as theoperating frequency of the igniter 4 remains constant, the time delaywill be accurate. Experiments have shown that time delays of up to 5seconds, accurate to better than 1 millisecond, can be obtained even ifthe operating frequency of the igniter 4 is only accurate to + or −20%.

In a second embodiment of the igniter 4, the operating frequency isdetermined by a more accurate crystal rather than a resistor andcapacitor. As a result, the calibration process is not necessary inorder to produce accurate time delays. However, the calibration processcan still be used in order to verify the proper operation of igniter 4and to verify that the oscillator frequency of igniter 4 is consistentwith the crystal.

Having completed the evaluation of all igniters 4 connected to theoutput ports, the interface module 20 then enables all output ports notpreviously disabled, turns on the respective “Ready” lights 24 on frontpanel 50 and provides a closed circuit at input current detector 51 thatcan be detected from control panel 11 as “continuity”. This provides thepyrotechnic operator with remote indication (at control panel 11) of thestatus of all ports of interface module 20.

Interface module 20 next enters a program loop whereby it continuouslylooks for the receipt of a valid “fire” command at input currentdetector 51. Upon receipt of a “fire” command, interface module 20confirms that the respective output port has not been disabled throughfailure of any previous test and validation sequence.

If the output port has not been disabled, interface module 20 issues an“arm” command to all igniters 4 attached to the respective port andwaits for confirmation from all igniters 4 attached to that port thatthey have received a proper “arm” command and have entered the armedstate. If any failure occurs in an igniter 4, interface module 20 willdisable the respective port and indicate a “fault” on front panel 50.

For all armed ports, the interface module 20 next issues a “fire”command. Upon receipt of a “fire” command, each igniter 4 evaluates the“fire” command to ensure that it meets all protocol requirements. If the“fire” command does not meet protocol requirements, the igniter 4 willreturn a “fault” command and immediately disable itself. If the “fire”command does meet protocol requirements, the igniter 4 will-fire lifte-match 5 and immediately check to see if the data/power cable has beendisconnected, an expected result of the shell having lifted and brokenthe cable. Should the igniter 4 detect that it is still connected to theinterface module 20, it will assume that the lift charge failed toignite, return a “fault” command to interface module 20 and immediatelydisable itself. If the igniter 4 does detect a successful disconnect, itwill enter its timing sequence until it reaches the programmed delay,upon which it will fire its break e-match 6 match, thereby igniting thepyrotechnic break charge and causing the shell to appear in the sky.

After the break e-match 6 ignites the break charge, the entire igniter 4will be destroyed. However, in case the ignition did not occur, igniter4 will wait a short period of time and then apply high current loads tothe igniter's microprocessor output ports in order to discharge energystorage element 42. In this manner, the source of energy to ignite breake-match 6 will be eliminated and the possibility of a late ignition ofthe break charge, termed a “hangfire”, will be greatly reduced.

As an additional safeguard, the interface module 20 monitors the currentflow through all ports which have been issued a “fire” command. If itdetects any igniters 4 still connected, it will disable that port andsignal a “fault” condition on front panel 50 in order to notify thepyrotechnic operator that a particular mortar still holds a livepyrotechnic projectile 1.

Detailed Circuit Of One Form Of Igniter

FIG. 6 shows the detailed circuit schematic for igniter 4 for oneembodiment of the present invention. Capacitor C1 provides protectionfrom electrostatic discharges or any other voltage transients that mayoccur on the input wires at connector J1. Diode pairs D1 and D2 areconfigured as a full wave rectifier and ensure that the voltage thatappears at the cathode of D2 is always positive. The use of diode pairsD1 and D2 allows the pyrotechnic operator to connect the two wires forigniter 4 without regard to polarity. Resistor R1 limits the currentinto capacitors C5 and C6, which are isolated from each other by dualdiode D3. When an input voltage of nominally 12 volts appears on theinput wires at connector J1, the C5 and C6 capacitors begin to chargeup. Capacitor C5 provides energy storage for the break e-match 6, whichwould be connected to igniter 4 at connector J2. Thus capacitor C5 isenergy storage element 42 previously discussed and shown in FIG. 3.Capacitor C6 provides energy storage for lift e-match 5, which isconnected to igniter 4 at J3. The use of capacitor C6 ensures thatsufficient peak current will be available to ignite lift e-match 5 eventhough resistor R1 and any additional wire resistance in the input wireswould otherwise limit the current available. Darlington transistor Q2provides an electronic switch to connect break e-match 5 to capacitorC5. Resistor R2 connects output pin 8 of microprocessor U1 to the baseof transistor Q2. Thus resistor R2 allows microprocessor U1 to ignitethe break e-match 5 by applying a five-volt signal to output pin 8 andturning on transistor Q2. Resistor R4 ensures that transistor Q2 willnot be accidentally turned on when the output pin 8 of microprocessor U1is initially open-circuited during the power-on initialization ofmicroprocessor U1. Transistor Q3 provides an electronic switch toconnect lift e-match 5 to capacitor C6. Resistor R3 connects the base oftransistor Q3 to output pin 7 of microprocessor U1. Thus microprocessorU1 can fire the lift e-match 5 by applying a five-volt signal to pin 7.Resistor R5 ensures that transistor Q3 will not be accidentally turnedon when output pin 9 of microprocessor U1 is initially open-circuitedduring the power-on initialization of microprocessor U1. Resistors R7and R12 provide a resistor divider to monitor the voltage on thecollector of transistor Q2. If capacitor C5 is charged, the voltage atthe collector of transistor Q2 will be approximately 10 volts if breake-match 6 is connected properly. If break e-match 6 is broken or if thewires to break e-match 6 are disconnected, the voltage at the collectorof transistor Q2 will be approximately zero volts. Thus, the use ofresistors R7 and R12 allows microprocessor U1 to determine if the breake-match 6 is operational by monitoring the voltage at input pin 9. In asimilar manner, resistors R8 and R13 allow microprocessor U1 todetermine the status of lift e-match 5 by monitoring the voltage on pin6 of microprocessor U1.

Voltage regulator U2 provides a constant five-volt output at pin 3.Capacitor C4 provides a small amount of energy storage to ensure thatwhen the break e-match 6 is ignited, the sudden load on capacitor C5does not disturb the power source for microprocessor U1. Voltageregulator U2 is necessary because the operating frequency of theparticular type of microprocessor, a PIC16C505, varies as the voltage atpin 1 of microprocessor U1 changes. Thus, voltage regulator U2 ensuresthat the operating frequency remains constant and that the accuracy ofthe time delay is maintained even if the voltage on capacitor C5 varies.Resistor R14 and capacitor C3 are the components that determine theoperating frequency of microprocessor U1. As previously discussed, theaccuracy of the time delay is improved by the timing calibrationprocess.

The connection of pin 3 of microprocessor U1 to ground allowsmicroprocessor U1 to rapidly discharge capacitor C5 by trying to drivepin 3 to 5 volts. The high current at the output port pin 3 will causethe supply current at pin 1 to increase. This in turn will cause ahigher load current for the voltage regulator U2 and will dischargecapacitor C5.

Resistors R1 and R6 form a resistor divider that allows microprocessorU1 to sense a successful launch of the pyrotechnic projectile 1. As longas power is applied to igniter 4 through connector J1, the voltage atpin 11 of microprocessor U1 will be five volts. However, when the liftcharge is ignited and the shell is launched, wires 7 will break. At thispoint, the voltage at pin 11 of microprocessor U1 will drop to zerovolts, and can be detected by microprocessor U1.

Communication Between Igniter And Interface Module

Transistor Q1 and resistor R15 provide a means of communication fromigniter 4 to interface module 20. Capacitor C2 and resistors R9 and R10provide a means of communication from interface module 20 to igniter 4.The operation of this method of bi-directional communication over asingle pair of wires, that also supply power, is best understood bylooking at FIG. 7. Interface module 20 contains components Dx, Rx andSwx. Dx is a diode that provides the source of power (12 volts) forigniter 4 through wire 7 a. Wire 7 b provides a ground return path tocomplete the power connection. Switch Swx, under control of themicroprocessor in interface module 20, momentarily closes, causing thevoltage at the cathode of diode Dx to become 20 volts. The quiescentvalue of the voltage at point B is nominally zero volts. When switch Swxcloses, the 8-volt increase in the voltage on wire 7 a is coupled bycapacitor C2, through resistor R9, to point B. Thus, the voltage atpoint B will increase by 8 volts whenever switch Swx is closed, and willreturn to zero when switch Swx is opened. Resistor R9 ensures that anyover-voltage at point B, which is connected to an input pin ofmicroprocessor U1 of FIG. 6, does not adversely affect microprocessor U1Resistor R9 further ensures that if the voltage at B becomes less thanzero, microprocessor U1 is not adversely affected. Note that resistorR1, in conjunction with capacitor C5, reduces the switch current atswitch Swx and further reduces any voltage change on capacitor C5 due tothe low-pass filter nature of the circuit. Thus, pulses in the range of1 microsecond to 100 milliseconds can be easily sent from interfacemodule 20 to igniter 4 with the particular component values chosen forthe circuit. Communication in the reverse direction (from igniter 4 tointerface module 20) is accomplished with components transistor Q1,resistor R15 and resistor Rx. The voltage at point A is normally fivevolts and transistor Q1 is off. At that point, the current in wire 7 asupplies the operating current for igniter 4, which is a relativelysmall and constant value. As a result, Vx, the voltage across resistorRx, is also a relatively small and constant value. When the voltage onpoint A is pulsed to zero volts, additional current flows throughtransistor Q1, causing the voltage across resistor Rx to increase. Thisincreased current may be smaller than, or even much higher than, thenominal operating current for igniter 4. By monitoring voltage Vx, themicroprocessor in interface module 20 can receive information fromigniter 4 by using pulses at point A in the range of 1 microsecond to100 milliseconds. Note that diode D3 prevents any current in transistorQ1 from being drawn from capacitor C5. Thus bi-directional pulsedcommunication can be accomplished with a pair of wires which are alsosupplying power. Not shown in FIG. 7 are the two diode pairs D1 and D2in FIG. 6 which form the full wave rectifier and allow wires 7 a and 7 bto be connected in reverse to igniter 4. Diodes D1 and D2 do notadversely affect the bi-directional communication method.

Detailed Circuit Of Alternative Form Of Igniter

FIG. 8 shows the detailed schematic of igniter 4 in a second embodimentof the present invention. This version of igniter 4 is quite similar tothe embodiment of FIG. 6 in a number of ways. The similarities includethe input protection, full wave rectifier, energy storage, voltageregulation, and lift e-match 5 and break e-match 6 drivers.

The schematic of FIG. 8 differs from that of FIG. 6 in the followingways. First, there is no provision for bi-directional communicationbetween igniter 4 and interface module 20. Second, igniter 4 uses adifferent firing protocol from interface module 20. This protocol, usedby the Fire One Computerized Fireworks Shooting System from PyrotechnicsManagement, Inc., State College, Pa., provides 12 volts for testingcontinuity (that is, presence of either an igniter 4 or a lift e-match5) and 24 volts for firing the igniter 4 or lift e-match 5. ResistorsR13 and R14 form a resistor divider to detect the 24-volt firing signal.Resistors R4 and R5 form a second resistor divider that detects asuccessful launch by removal of the input voltage. Diode D9 and resistorR15 provide clamping to ensure that the input pin that detects powerloss (microprocessor U1 pin 11) does not become damaged when the inputvoltage increases to 24 volts to signal the fire command. Q3 is acrystal that provides increased accuracy over the resistor-capacitoroscillator of the FIG. 6 circuit. Capacitors C1 and C2 are required bythe internal crystal oscillator of microprocessor U1. Resistors R2 andR3 provide a resistor divider that is used to measure the voltage oncapacitor C4, the energy storage element 42. Upon receipt of a firecommand, microprocessor U1 checks that the voltage on capacitor C4 issufficient to provide enough energy to ignite break e-match 6 beforeigniting lift e-match 5. The schematic of FIG. 8 thus represents anigniter 4 that provides increased safety and timing accuracy but doesnot use extensive communication capability. Thus FIG. 8 describes anigniter that appears more like a conventional electric match but withincreased safety and timing accuracy.

1. An igniter for a pyrotechnic projectile of the sort comprising a liftcharge to be ignited by an electrically operated lift charge ignitiondevice, and a break charge to be ignited by an electrically operatedbreak charge ignition device, said igniter comprising: electroniccontrol means for receiving an electronic fire command from an externalcontrol device and, in response thereto, (1) activating saidelectrically operated lift charge ignition device, and (2) apre-determined time after receiving said electronic fire command,activating said electrically operated break charge ignition device. 2.An igniter according to 1 wherein said electronic control means furthercomprise: means for preventing transient voltages from unintentionallyactivating said electrically operated lift charge ignition device andsaid electrically operated break charge ignition device.
 3. An igniteraccording to 1 wherein said electronic control means further comprise:means for ensuring that the polarity of said electronic control means ismatched to the polarity of said external control device.
 4. An igniteraccording to 1 wherein said electronic control means comprise: a firstoutput connecting said igniter to said electrically operated lift chargeignition device; a second output connecting said igniter to saidelectrically operated break charge ignition device; a power supply forselective connection to said first output and said second output forselectively activating said electrically operated lift charge ignitiondevice and said electrically operated break charge ignition device,respectively; and a timer for determining when said power supplyactivates said electrically operated break charge ignition device.
 5. Anigniter according to 4 wherein said power supply comprises at least onecapacitor.
 6. An igniter according to 4 wherein said timer comprises aresistor/capacitor combination.
 7. An igniter according to 4 whereinsaid timer comprises a crystal.
 8. An igniter according to 4 whereinsaid timer is accurate to within 0.001 seconds.
 9. An igniter accordingto 1 wherein said electronic control means further comprise: means formonitoring the status of said electrically operated lift charge ignitiondevice and said electrically operated break charge ignition device. 10.An igniter according to 1 wherein said electronic control means furthercomprise: means for sensing a failure to achieve a proper launch of saidpyrotechnic projectile and, upon sensing such a failure, preventingactivation of said electrically operated break charge ignition device.11. A pyrotechnic projectile comprising: a lift charge; an electricallyoperated lift charge ignition device for activating said lift charge; abreak charge; an electrically operated break charge ignition device foractivating said break charge; and an igniter comprising electroniccontrol means for receiving an electronic fire command from an externalcontrol device and, in response thereto, (1) activating saidelectrically operated lift charge ignition device, and (2) apre-determined time after receiving said electronic fire command,activating said electrically operated break charge ignition device. 12.A pyrotechnic projectile system comprising: a pyrotechnic projectile andan external control device; said pyrotechnic projectile comprising: alift charge; an electrically operated lift charge ignition device foractivating said lift charge; a break charge; an electrically operatedbreak charge ignition device for activating said break charge; and anigniter comprising electronic control means for receiving an electronicfire command from said external control device and, in response thereto,(1) activating said electrically operated lift charge ignition device,and (2) a pre-determined time after receiving said electronic firecommand, activating said electrically operated break charge ignitiondevice.
 13. A pyrotechnic projectile system according to 12 wherein saidexternal control device comprises: means for detecting if said igniterof said pyrotechnic projectile is connected to said external controldevice.
 14. A pyrotechnic projectile system according to 12 wherein saidexternal control device comprises: means for communicating with saidigniter.
 15. A pyrotechnic projectile system according to 12 whereinsaid external control device comprises: means for detecting a fault insaid igniter and, upon detection of the same, deactivating said igniter.16. A pyrotechnic projectile system according to 12 wherein saidexternal control device comprises: means for providing a calibrationsignal to said electronic control means.
 17. A pyrotechnic projectilesystem according to 12 wherein said external control device comprises:means for detecting a fire command from an external user interface and,upon detection of the same, issuing an electronic fire command to saidigniter.
 18. A pyrotechnic projectile system according to wherein saidexternal control device comprises: means for detecting if saidpyrotechnic projectile has properly launched in response to receivingsaid electronic fire command and, if not, for disabling said pyrotechnicprojectile.
 19. A pyrotechnic projectile system according to 12 whereinsaid external control device comprises: an interface module adapted tobe connected to a manual control panel.
 20. A pyrotechnic projectilesystem according to 12 wherein said external control device comprises:an interface module adapted to be connected to a computer.
 21. Apyrotechnic projectile system according to 12 wherein: said systemcomprises multiple pyrotechnic projectiles, said system comprises aport, and further wherein multiple pyrotechnic projectiles are connectedto said port, each of said pyrotechnic projectiles being separatelycontrollable by said system.
 22. A pyrotechnic projectile systemaccording to 21 wherein said system is adapted to detect when the numberof pyrotechnic projectiles connected to said port exceed a predeterminednumber.
 23. A method for firing a pyrotechnic projectile, said methodcomprising the steps of: sending a “fire” command to said pyrotechnicprojectile so as to activate a lift charge; upon receiving confirmationof a successful launch, electrically timing a delay within saidpyrotechnic projectile; and upon expiration of said delay, detonating aburst charge carried by said pyrotechnic projectile.
 24. A methodaccording to 23 wherein, upon failure to detect said launchconfirmation, deactivating said projectile.
 25. A detonator fordetonating an explosive charge, said detonator comprising: electroniccontrol means for receiving an electronic fire command from an externalcontrol device and, a pre-determined time after receiving saidelectronic fire command, detonating said explosive charge.
 26. Apyrotechnic projectile system according to 12 further comprising: asecond pyrotechnic projectile comprising: a lift charge; an electricallyoperated lift charge ignition device; a break charge; a fuse foractivating said break charge, said fuse being activated by saidelectrically operated lift charge ignition device.
 27. A pyrotechnicprojectile system according to 12 wherein said external control devicecomprises: means for detecting a fault in said igniter and, upondetection of the same, providing notification to the system operator.28. A pyrotechnic projectile system according to 16 wherein saidcalibration signal is a time calibration signal.
 29. A pyrotechnicprojectile system according to 18 wherein said external control devicefurther comprises: means for notifying the system operator if saidpyrotechnic projectile is disabled.
 30. A method according to 23 furthercomprising: prior to sending said “fire” command to said pyrotechnicprojectile, sending a calibration signal to said pyrotechnic projectileand, upon receiving confirmation of proper calibration, sending said“fire” command to said pyrotechnic projectile.
 31. A method according to23 further comprising: prior to sending said “fire” command to saidpyrotechnic projectile, sending an “arm” command to said pyrotechnicprojectile and, upon receiving confirmation of the armed status of saidpyrotechnic projectile, sending said “fire” command to said pyrotechnicprojectile.
 32. A pyrotechnic projectile system according to 12 whereinsaid pre-determined time is pre-programmed into said igniter.
 33. Apyrotechnic projectile system according to 12 wherein said externalcontrol device comprises: means for programming said pre-determined timeinto said igniter.
 34. A method according to 23 wherein the magnitude ofsaid delay is pre-programmed into said pyrotechnic projectile.
 35. Amethod according to 23 wherein the magnitude of said delay is programmedinto said pyrotechnic projectile at the time of use.
 36. A pyrotechnicprojectile system according to 26 wherein said system is adapted todetect when the total number of said pyrotechnic projectiles and saidsecond pyrotechnic projectiles connected to said port exceed apredetermined number.
 37. A pyrotechnic projectile system comprising: aplurality of pyrotechnic projectiles and an external control device;each of said pyrotechnic projectiles comprising: a lift charge; anelectrically operated lift charge ignition device; a break charge; and afuse for activating said break charge, said fuse being activated by saidelectrically operated lift charge ignition device; said external controldevice comprising a port, with said plurality of pyrotechnic projectilesbeing connected to said port, and said external control device beingadapted to detect when the number of said pyrotechnic projectilesconnected to said port exceed a predetermined number.